Local adipocytes enable estrogen-dependent breast cancer growth

The importance of the microenvironment in breast cancer growth and progression is becoming increasingly clear. Adipocytes are abundant in the mammary microenvironment, and recent studies show that adipocytes produce endocrine, inflammatory, and angiogenic factors that have tremendous potential to affect adjacent breast cancer cells. Yet, the extent to which local adipocyte function contributes to the pathogenesis of breast cancer is largely unexplored. Here we describe a unique animal model to study interactions between adipocytes and breast cancer cells in the tumor microenvironment. Our results suggest that local interactions between adipocytes and tumor cells are sufficient to promote the growth of hormone-dependent breast cancer. We also demonstrate that leptin signaling in adipocytes induces aromatase expression, expected to result in higher estrogen in the microenvironment thus enabling mammary tumorigenesis.